The spectral absorption coefficients of total particles a_p(λ), nonalgal particles a_d(λ) and phytoplankton a_ph(λ) in Xin'anjiang Reservoir(Lake Qiandao) were studied based on the data of 53 sampling sites in the summer of 2013. The results showed that the absorption spectra of total particles were similar to those of phytoplankton except the data at sites 9 and 10. It indicated that phytoplankton made larger contribution to the total particles. The values of the total particulate matter at 440nm a_p(440) ranged between 0.068 and 0.629 m^-1 in the water body. Moreover, the values of a_p(λ) in the northwestern area were significantly larger than those in other areas, while the values of a_p(λ) in the lake district and the southwestern riverine areas were the smallest. Absorption coefficients of nonalgal particles decreased exponentially from the short to the long wavelength. There were marked spatial variations of the exponential spectral slope coefficients of nonalgal particles S_d with the average value of 8.52±1.62μ m^-1. However, the values of S_d in Xin'anjiang Reservoir were generally low due to the low values of the inorganic suspended solids. Significant positive relationships were found between a_d(440) and phytoplankton pigment concentrations, suggesting that the degradation of phytoplankton was an important source of the nonalgal particles in summer. There were distinctive absorption peaks at the wavelength of 440 and 675nm in the absorption spectra of phytoplankton. In addition, there were significant spatial variations of the phytoplankton absorption coefficients at 440nm (a_ph(440)) and 675nm (a_ph(675)). Significant positive linear relationships were found between a_ph(440), a_ph(675) and phytoplankton pigment concentration, respectively, while weak relationships were showed between a_ph(440), a_ph(675) and the total suspended solids, respectively.